Method for drying thin cellulose sheets



uid, means to hold said liquid, a floating body within the liquid provided with a hollow space, a liquid within said hollow space, means to spin said holding means and the two liquids and the floating body, a second floating body within the second liquid, which thus will be capable of moving in one direction or the other along a path substantially parallel to the spinning axis of the second liquid whenever said axis is deflected relativelytothe horizontal and means to provide a second floating body with a restoring tendency which will tend to return said floating body to its predetermined normal position whenever displaced therefrom.

In testimony whereof I aflix my signature.

' RODRIGO M. SMYTH;

1932- c. H VON HOESSLE ET AL 9 8 METHOD FOR DRYING THIN CELLULOSE SHEETS Filed Dec. 6, 1930 2 Sheets-Sheet 1 FIG 1 VON HOESSLE BY Ono MARTIN ScHADE 1 c. H. VON HOESSLE ET AL 3 3 2 METHOD FOR DRYING THIN CELLULQSE SHEETS Filed Dec. 6, 1930 2 Sheets-Sheet 2 ANVENTORS CARL ERMANN vou HOESSLE BYOTTO MARTIN SCHADE ATTQRNEY Patented Dec. 13, 1932 UNITED STATES PATENT CARI: WIN vox HOESSLE AND OTTO IABTIN SCHADE, O1 BLDEBEUL-DRESDEN, GERMANY, ASSIGNOBS TO OKEMISCHE FABRIK VON HEYDEN, A. G., OF RADEIBEUL NEAR DBIESDEN', GERMANY, A CORPORATION OF GERMANY METHOD FOR DRYING THIN CELLULOSE SHEETS,

Application filed December 6, 1930, Serial No.

Applications have been filed in Germany on Nov. 8, 1924 Nov. 28, 1925; Nov. 30,1925; Apr. 28, 1925; and Jan. 29, 1927; and of which the following is a specification.

This invention relates to a method of drying thin sheets of cellulose and it particularly relates to the drying of long continuous webs of cellulose made of viscose, the object of the invention being to provide means which will allow to evenly dry such-webs without causingthe same to create undulations in the web whereby it is impossible to bring thesame on the market in proper form.

The drying of thin pellicles, of cellulose, for instance made of vlscose, is difiicult because such thin pellicles of cellulose are not only highly sensitive in their mechanical handling but are also subject to an enormous shrinkage during the drying process.

These difiiculties have created a considerable prejudice among the men of the art in that these webs of cellulose should only be passed through the drying apparatus with the greatest care so as to subm1t them to as little strain as possible. After the infancy of this industry, in which carrier belts, ropes, etc. were used for transporting the web, the wet cellulose webs are passed today in all drying machines over horizon-- tally arranged cylinders, or rolls, of which there were usually two series, the cylinders of one being arranged above those of the other so as to have its individual cylinders disposed in the interstice between two ad.- joining cylinders of the lower series, the web being thus passed alternately from a lower to an upper cylinder and so on withou't actually undergoing'any but a minimum of strain. The prevailing prejudice did not dare to put the web to a greater strain than required to adhere in its travel to the surface of the adjoining rotating cylinders. The climbin of the web in the arrangement of the rollers in A-shape fashion was still effected in the same way from one roll to another as in the horizontal arrangements of the cylinders.

These arrangements had considerable shortcomings on account of the pockets 600,559, and in Germany November-8,1924.

formed by the adjoining cylinders, in which pockets t e air was stagnating, thereby delaying the drying. It required cumbersome mechanical contrivances to cause a continuous flow of the drying air around the drying cylinders and even then it was extremely hard to pass an air-current of an even temperature over all parts of the web. Owing to this bad regulation of the temperature inferior products were often the result.

Even the adoption of a distance between each of the drying cylinders, from the paper of space is often prohibitive, all the more as its spaciousness, also entails great costs of operation.

'Aforesaid considerable shortcomin have induced us to study the behavior of t e web from its first wet state to its ultimate dry end. Though the prior art knew that a web shrinks consi erably during its drying and that it does not shrink uniformly over its surface, the prejudice prevailing'm the vented the observation, made us during our studies, that the web actua 1y does not shrink at all in the first stage'of the drying process while it still has aconsiderable content of moisture. In view'of the absence of any noticeable shrinkage in the initial stage it over a plurality of cylinders arranged in a stack vertically one above the otherybe'cause the downwardly directed, sinuous] apath,

prior art prewhich the web is thus forced to take, allows the phenomena, occurring during the drying process and causing the undulations of the web, to counteract each other with the result that a perfectly smooth web of cellulose is obtained. 4

Other features of the invention will appear as the specification proceeds.

As an example of how to carry our invention into efiect we shall describe below and illustrate in the accompanying drawings one set of vertically arranged cylinders we found advantageous in the operation of our in vention.

In the drawings: Fi 1 is a vertical section through one set oii'cylinders;

Fig. 2 is a vertical section through a modified set of cylinders;

ig. 3 is a plan view of the ap aratus; Fig. 4 is an end elevation; and Fig. 5 shows a combination of two driers.

In said drawings Figure 1 is a vertical sec-.

tion-throughone set of cylinders, showing a plurality of for instance six cylinders, 1, 2, 3, 4, 5 and 6 arranged in a suitable frame (not shown), one cylinder being superimposed upon the other; a gearing 7 engages a suitable gearing (not shown) of the cylinder 1 an causes the same to rotate in the direction of the arrow 1 thereby imparting motion to all the uppercylinders in the direction of the arrows alon the peripheral face of each of the same. aring 7 is co-operatively engaging the cylinder 8, serving as a reel, by a suitable connection, for instance alsprocket wheel chain drive 9, engaging suit- .7 together with the cylinders 1-6 is 'encase water or the like e sprocket wheels 10 and 11 arranged on the axles of the gearing 7 and cylinder 8,

'vely, and indicated in dashed lines.

e vertical arrangementofthe gearin bya housing 12 --made of any suitable ma-. terial; it has attheibottom an air inlet 13 and at the to an outlet 14; openings 15 and 16 are provi ed at the top and near the bot-.

tom for the inlet of the wet and the outlet for the web, respectively. A radiator 17 is provid inside the housing 12 above the air inlet; the radiator is fed with steam, hot

agents to heat the air comfrom below.

the operation'of our method of dryingthewebthesameispassed-inthe wetstate,

coming either directly from the treating tanks, in which it was purified, or from a roll (both-tanks and roll not shown), over the c lindcr 6 and is then passed downward from o same over the cyhnders 5- -1; it is then transferred to and wound up by the cylinder 8 where it arrives in the state.

Owing to the motion imparted, to the cylinder 1, a. pulling. or stretching ei fect is exerted on the web which extends to it over all the cylinders up to the cylinder 6.

By this arrangement we succeed in drybeneficial to exert a pressure upon the'web' to reduce its shrinkage, this was done by having) ne or more rotar cylinders roll upon the we We have foun that this weighting of the web is very helpful in reducing the.

thickness of the web, it desired, by squeezing the web and to assist in stretching the web in co-operation with an adjoining roller, but it is without any material help in the beginning of the drying process, except for re ucingthe thickness of the web by slmply squeezing it, which to do is not always advisable because the web is easily aifected by the surface of the cylinders.

A desirable bilaterally acting suction effect of the air current is obtained if we move the bearings of the cylinders apart from each other so as to create an interstice between the adjoinin cylinders as illustrated by Figure 2, which s ows a vertical sectional View of a slightly difierently arranged stack.

We thus freely ex se both sides of the web to the warm 8.11 w en moving through those interstices. This arrangement of the cylinders. with'an interstice between each of them has the advantagethat the web, being dried evenly .irom both sides, dries ve much a quicker; moreover the possibility 0 having the web aflected by the surface of the e linders, is reduced. Inasmuch as the mo e of driving the cylinders is practically the same as in t e case of the arrangement with partly free and artly journaled rollers, we do not describe this feature because of being within the skill of a mechanic.

It is by no means necessary to have the interstice between the cylinders of the same length. In view of the non-shrinkage of the wet web in theinitial-stage of the drying process we arran e that the'web passes first over a number o cylinders which are relatively far apart from each other. soon as a certain amount of moisture has evapocylinders to each other so as to have in the "last stage with the greatest shrinkage only .a small, or no interstice between the cylinrated the shrinkage becomes noticeable and the more the drying process'and the shrinkage increase the nearer we bring then the 

